1. Field of the Invention
The present invention relates to a lens barrel holding apparatus used for mounting a lens barrel on a tripod, a lens barrel held (or supported) by the lens barrel holding apparatus and a camera system.
2. Related Background Art
There are the following types of lens barrel holding apparatuses used as a mounting pedestal for mounting the barrel of an interchangeable lens on a tripod.
(A) A lens barrel holding apparatus in which a ring shaped barrel mount part surrounding the lens barrel is fastened with screws disposed in radial directions with respect to the optical axis of the lens barrel directly or with a cushioning member between.
(B) A lens barrel holding apparatus in which a slit is formed on a portion of a ring shaped holding member and the opposed portions thereof that face the slit are fastened by a screw with a required fastening force to hold the lens barrel.
(C) A lens barrel holding apparatus in which two arc-shaped holding members are pivotably joined at their one ends so that the holding members can be opened to receive the lens barrel inside the holding members and fastened with a clamp screw to hold the lens barrel. On the occasion of the hand-held shooting, it is possible to dismount the lens barrel form the lens barrel holding apparatus by loosening the clamp screw.
(D) A lens barrel holding apparatus in which a ring portion for holding the lens barrel and for adjusting its revolving position and a pedestal portion to be fixed on a tripod are detachable.
(E) A lens barrel holding apparatus in which two arc-shaped holding members are pivotably joined at their one ends so that the holding members are opened to receive the lens barrel inside the holding members. In addition, the lens barrel is adapted to be securely held by turning an eccentric cam provided on one of the holding members while it is in contact with a wall of the other holding member.
However, the above-described lens barrel holding apparatus (A) suffers from the following disadvantages (a) to (d).
(a) Since a heavy load is applied on the position on the lens barrel (or the barrel mount part) at which the screw impinges, the lens barrel can be easily deformed. Therefore, it is necessary to reinforce the lens barrel that is to be mounted on the lens barrel mount part.
(b) The load of the lens barrel is applied along the line connecting a screw and another screw disposed at the position opposite to that screw with respect to the optical axis, and backlash is likely to be produced in the direction perpendicular to this line.
(c) If the screw is not tightened sufficiently, the lens barrel will incline relative to the holding apparatus.
(d) When the lens barrel is to be detached from the lens barrel mount part, it is necessary to take out the lens barrel from the barrel mount part after separating the lens barrel and the camera, since the barrel mount part has an integral ring-like shape.
In the case of the above-described lens holding apparatus (B), although it is free from the load concentration and other disadvantages thanks to the slit structure, it still suffers from the above problem (d) upon detaching the lens barrel, since the holding member is of a ring-like shape.
Furthermore, in the case of the above-described lens barrel holding apparatus (C), it is necessary to turn the clamp screw a significant number of times upon attaching/detaching the lens barrel. Thus, the operability is bad, and the lens barrel cannot be attached or detached quickly.
In the case of the above-described lens barrel holding apparatus (D), since the lens barrel is secured by tightening the clamp screw serving as means for fixing the rotational position of the lens barrel, the problems same as problems (a) to (c) of lens barrel holding apparatus (A) arise.
In the case of the above-described lens barrel holding apparatus (E), since the two holding members are drawn in by the eccentric cam, it is necessary to generate a sufficient lens barrel securing force while rotating the eccentric cam to a position at which a sufficient frictional force is produced so as to prevent the eccentric cam from being returned backwardly by the load of the lens barrel held. Accordingly, it is required to achieve a significant fastening force of the holding members and a high machining precision that enables alignment of the rotational position of the eccentric cam. Furthermore, durability of the parts is also required so that the above-described setting will not change with the lapse of time. In addition, if the fastening force of the holding members is weak, the aforementioned problems (b) and (c) arise inevitably.